An anemometer is a device which measures the velocity and direction of fluid flow. A solid state microanemometer is disclosed in applicant's U.S. Pat. No. 4,930,347, a patent that is commonly owned by the assignor of this application. Basically, the solid state microanemometer disclosed in U.S. Pat. No. 4,930,347 relies upon substantial thermal and electrical isolation of the resistor legs to provide high temperature sensitivity and fast response time. This device is readily adaptable for use in a wide variety of applications. For instance, an array of these devices may be connected to associated computer interfaces to provide "intelligent" sensing of microflow patterns for medical, industrial or other applications.
For many applications, it is necessary for an anemometer to withstand varying degrees of mechanical vibration over a long period of time. Otherwise, frequent breakage would necessitate excessive material and labor costs associated with replacement. Especially in sensing liquid flow, solid state anemometers seem to be particularly susceptible to conditions of mechanical or physical wear.
In short, the success of a solid state anemometer depends not only upon its high temperature sensitivity and fast response time, but also upon its ability to maintain these qualities under conditions of mechanical stress over a period of time.
Moreover, it is known that raising the operating temperature of an anemometer increases its sensing capability. For an anemometer of the type shown in U.S. Pat. No. 4,930,347, which utilizes self-heating resistors, this would suggest operation of the device at a higher current to increase the operating temperature of the resistors. However, because the self-heating resistors are interconnected by silicon, which has a high thermal conductivity, an increased current magnifies thermal shorting between the resistors, and thereby diminishes the capability of the device to detect small temperature differences. This capability is necessary for accurate sensing of fluid flow direction.